Process of refining vegetable oils



Dec. 17, 1940. H. M. DUVALL JR PROCESS OF REFINING VEGETABLE OILS FiledJune 25, 1938 Patented Dec. 11, 1949 UNITED muss,

PATENT OFFICE 2,225,557 I PROCESS or Rename VEGETABLE OILS Howard -M,Duvall, Jr Jackson Heights, N. Y.,

assignor to Refining, Inc., Reno, Nev., a corporation of Nevada Y,Application June 23, 1 938,'ScrialNo.215,463 Y 9 qlaims. r01; 260-425)This invention relates to a process ofr efining vegetable and animaloils-and more particularly to a process in which at least a portion of.the gums are removed prior to neutralization.

An object of the invention is to provide a process of refining vegetableoils in which effective separation of soap stock from the oil isaccomplished after at least a portion of the minor constituents or gumshas been removed from thejoil;

In the alkali refining of so-called degummed oils," it has been foundextremely difiicult, if not impossible, to consistently secure aneffective separation of the soap-stock from the oil. If the conventionalbatch method of alkali refining oils is employed, the soap stockfractionates, that is, when the soap stock settles, a liquor which ispredominantly water separates from the soap thereof as the lower ornigre layer, the soap in'admixture with a large proportion'of theneutral oil forms an intermediate layer, and the remainderor the neutraloil forms the upper layer. A clean separation of soap from neutral oilis therefore not possible. This has prevented the successful refining ofdegummed crude oil by the batch method. Substantially the same thingmany times happens in continuous refining. The nigre along with some ofthe soap discharges from the of the soap stockabove referredtoisxprevented,

and a clean separation can be effected; Apparently the gums or minorconstituents, contained in the original crude act as'emulsifying agentsto prevent the fractionating, of the soap stock and all ofthe soap stock'is discharged as the heavy efliuent, providing a clean separationbetween the soap stock and the oil." Furthermore, an excessive amount ofminor constituents in the oil being refined causes an excessiveentrainment of neutral oil in the soap stock. By the present inventionthe amount of minor constituents, in the mixture subjected to alkalirefining, may. be adjusted to the optimum amount which will causeeffective separation with a minimum amount of oil entrained in the soapstock.

It is, therefore, an object of the present invention to provide aprocess of refining degummed oils in which a sufiicient amount ofundegummed oil is added to, the degummed oil to prevent stratificationof the soap stock.

Another object .of the invention is to provide a'process of refiningvegetable oils in which oil is first degummed to recover phosphatidesand other minor constituents and then mixed with a portion of undegummedoil and subjected to alkali refining to remove the free fatty acidsthereof. I I

A further object of the invention is to provide a process of refiningdegummed oils in which the oil is refined in admixture with a portion ofundegummed oils in order to effect continuous centrifugal separation ofthe soap stock from the oil. A still further object of the invention isto provide a process in which the amount of gums in the oil subjected toalkali refining is adjusted to provide an effective separation of soapstock from the oil with a minimum of oilentrained in the soap stock.

Other objects and advantages of the invention will appear in thefollowing description of the .preferred process given in conjunctionwith the attached drawing, which is a diagrammatic view of an apparatussuitablefor carrying out a continuous process in which the oil is firstdegummed andlthen admixed with a portion of undegummed oil and subjectedto alkali refining.

Referring to the drawing, a source of supply of crude vegetable oil isshown as a tank It); a source of supply of a gum precipitating reagentis shown as a tank II; and a source of supply of an alkali refiningreagent is shown as a tank l2. Oil. may be withdrawn from the tank illby a pump I3 and delivered through a meter l4 in the "pipedii and thencethrough one or more heat ex- .4 change. devices 16 to'a mixing device H.The heatjexchange' devices l6 preferably include coils I 8 through-whichthe oil is passed and casings lflthr'ough which any desired heatingmedium maybe circulated by the pipes 20 and 2|. The

heat exchange devices iii are employed to bring theoil to a mixingtemperature suitable for the particular oil being treated.

The tank II for the precipitating reagent may include "a heating coil 22in: order to bring the precipitating reagent to a temperature suitablefor mixing the same with the oil. The precipitating reagent may bewithdrawn from the tank I i by means of a pump 23 and delivered througha meter 24 to'the mixing device H. The mixing device I! may comprise anysuitable type of flow mixer which is capable of producing an intensemixing action between the oil and reagent, for example a closedmechanical agitator.

The mixture .of oil, reagent and precipitated gums is then preferablypassed through one or more heat exchange devices 25, which may beentirely similar to the heating devices IE, to a continuous centrifugalseparator 26. Precipitated gums including valuable phosphatides andother minor constituents are continuously discharged from centrifugal 26through a spout 21 into a receiver 28. These materials, particularlyfrom vegetable oils, form a valuable byproduct and may be furtherpurified to recover substantially pure phosphatides or may beemployed assuch in their crude state as phosphatidic materials.

The degummed oil is discharged from centrifugal 26 through a spout 29into a tank 30 which is preferably closed except for a vent 3| The tank30 may be relatively small and merely serves as a reservoir tocompensate for any slight differences in flow between different portionsof the process. The degummed oil may be withdrawn from the tank 30 bymeans of a pump 32 and delivered through. a meter 33 and a heat exchangedevice 34, similar to the heat exchange device l6, and a pipe 35 to anysuitable type of flow miser 35' at the junction of the pipe 35 with apipe 36 which delivers a portion of undegummed oil into the pipe 35. Thepipe 36 may receive undegummed oil from the pump l3 Val ter 4| to themixer 39. The refining reagent in the tank l2 may be brought to anydesired predetermined temperature suitable for mixing the same with theoil to be treated by means of a heating coil 43 positioned in the tankl2. The

mixer 39 may also be any suitable type of flow mixer. Since the alkalirefining reagent readily mixes with the oil, the intensity of mixing inthe mixer 39 may not be as great as that in the mixer i1. Soap stockisformed substantially as soon as the refining reagent contacts the, oilin the mixer 39 and a mixture of soap stock and oil is passed through aheat exchange device 44, similar to the heat exchange device I6, andthence to a continuous centrifugal separator 45. Soap stock isdischarged from the centrifugal 45 as the heavy effluent through a spout41 into a receiver 48, and refined oil substantially free of soap stockis discharged through the spout 48 into a receiver 49.

In the apparatus illustrated, proportioning has been shown as beingeffected by pumps and meters, but it is understood that any suitabletype of proportioning apparatus may be employed. The centrifugalseparators 26 and 45 are preferably of the heated type disclosed in thepatent to Benjamin Clayton, No. 2,100,277, issued November 23, 1937,since by the use of such heated centrifugals continuous discharge of theheavy effluent can be secured over extended lengths of time withoutcleaning of the centrifugal.

The temperature at which the oil and degumming reagent are delivered tothe mixer I! will depend upon the nature of the oil being treated.Certain oils respond to treatment with mixing at relatively hightemperatures, in which case the heating devices l9 may be employed tobring The mixture of degummed the oil to a predetermined temperaturesuitable for the particular oil being treated. with other amount ofgums, also depending upon the na-' ture of the 011 being treated. In thecase of either preheating, i. e., before mixing, or subse quent heating,any required number of heat exchange devices 25. may be employed tosecure .the correct time of treatment between mixing and separation.This time usually is found to lie between 5 and 15 minutes, but withexceptional oils may be less than 5 minutes or, in some cases, as longas 30 minutes. In general, the higher the temperature of treatment andthe smaller the amount of precipitating reagent employed, the shorterwill be the time between mixing and separation to effect maximumseparation of gums from a particular oil. Centrifugal separation of thegums from the oil is usually most efficient at temperatures between andF. Thus the heat exchange devices may be employed to either heat or coolthe mixture in order to secure the optimum temperature of separation.

The degumming reagent'may be water alone. but is preferably a relativelyconcentrated solution of anelectrolyte. Such concentrated solutions maybe neutral or slightly acid or slightly alkaline, but strongly acid oralkaline solutions should be avoided, since they will attack bothneutral oiland the'valuable constituents of the gums. lutions may beconcentrated solutions of neutral salts, such as sodium chlorlde,'withvery slight Such slightly acid or alkaline soamounts of strong acids oralkalies added therei to, in which case the pH of the solution shouldnot vary widely from neutrality. Preferably a concentrated solution of avery weak acid is employed and the preferred reagent is approximately al0% solution of boric acid. This solution. has a pH of approximately 3and not only precipitates more minor constituents than water or neutralconcentrated solutions, but in addition preserves the discharged gumsfrom fermentation or putrefactlon even after the boric acid has beensubstantially removed therefrom. The degumming reagent should beemployed in sufficientamount to precipitate the minor constituents andwet the oil, but excessive amounts will cause excessive entrainment ofoil with the gums. In most cases 2% is sufflcient but the amount willvary between 1 and 10% with different oils.

The heat exchange device 34 may be employed to either heat or cool thedegummed oil prior to alkali refining in order to bring the oil to a predetermined temperature for mixing, found most. suitable for theparticular oil being treated; Ash

in the case of the degumming step, the best temperature for mixing withthe alkali refining reagent will vary with the nature of the oil beingtreated, but will usually lie between 70 and 160 F. The lowertemperatures in this range are employed if the heat exchange device 44is emdevice 44 may be employed to provide time of treatment for colorremoval as well as for increasing or decreasing the temperature of themixture of oil and soap stock to bring it to the temperature found mostsuitable for separation in the centrifugal separator 45; Thistemperature must be sufliciently high that the emulsion which tends toform between the oil and soap stock is broken and will also vary withthe particular nature of the oil being treated, but will ordinarily liebetween 120 and 160 F.

The refining reagent may be employed in concentrations and amountsconforming to the recognized practices in the art of alkali refiningvegetable oils. amounts and concentration of the refining solution,which is ordinarily a caustic soda solution; will depend upon thefreefatty acid content of the oil as well as the type of oil beingrefined.

The amount of crude or undegummed oil added to the degummed oil in orderto secure effective separation of the soap stock during the refiningoperation will also vary with the nature of the oil being treated. Theamount of gums necessarily present in the mixture of oils to causeeffective separation of soap stock will usually increase with the freefatty acid content of the oils. The higher the free fatty acid content,the. more soap which is produced in the alkallrefining operation, and,in general, the greater amount of soap produced, the greater the amountof gums which are necessary to prevent stratification.

But other factors, such as the type of free fatty high free fatty acidcontent usually has a high gum content, but this is not invariable. Thusno definite proportions of crude oil to be added or gum contents in themixture of oil which are applicable to all oils can be given, but thecorrect amount of crude or undegummed oil to be added to a particularoil can easily be determined in running .the process. With oils that areextremelyv high in gums or minor constituents, only a small portion ofthe undegummed oil usually need be added to the degummed oil for theeffectiveseparation. As the amount of minor constituents in the crudeoil becomes less, a greater amount. of the crude oil should usually beadded to the degummed 011. For example, for cottonseed oils runningextremely high in minor constituents, say3% to 4%, only approximately10% of crude oil usually need be mixed with the degummed oil. For oilsrunning from 1% to il /2% of minor constituents, it may be necessary toadd suflicient crude oil to form a mixture of two-thirds degummed oiland one-third crude oil. n the other hand, for exceptional oils whichrun considerably less than 1% of minor constituents, it may at times benecessary to form a mixture containing as high as 90% of the untreatedor crude oil.

The present process is particularly adapted to the refining of vegetableoils such as, for example, cottonseed, soya bean, corn, sesame,cocoanut, and peanut oils, but in certain cases is found to beapplicable to animal oils. Thus the presentinvention provides a processof refining degummed oil'in which the soap stock may be separatedcleanly from the neutral oil. As was stated above, the alkali refiningof degummed oil has heretofore been impractical by the batch method andextremely difficult even with improved continuous processes. Inaddition, the present process not only provides for the recovery ofvaluable byproducts which would be damaged or destroyed if the crudeundegummed oil were directly alkali refined, but also markedly reducesthe refining losses over even improved continuous processes of directlyrefining the crude oil and over the total refining losses occasioned byfirst degumming the oil and then attempting to alkali refine the.degummed oil. For example, a crude oil containing 1% or more of minorconstituents and refined directly with alkali, withoutdegumming-frequently results in the production of soap stock containingfrom to of neutral oil. This same crude cottonseed oil, when two-thirdsof it is degummed with water or boric acid and then the remainingone-third of the crude mixed. with the degummed twothirds and themixture alkali refined by the continuous method, the free oil in thesoap stock from the alkali refining will run as low as 3% to 5% of freeoil. Since usually not more than 1% of free 011 is lost in the degummingoperation, it will be seen that a substantial saving in refining lossesis accomplished by the present process. It will further be seen that thepresent process allows the percentage of minor constitdetails thereof'maybe varied within the scope of the following claims.

I claim as my invention:

1 uents in the oil to be adjusted to that which will 1. The process ofrefining animal and vege table oils containing gums, which, comprisestreating said oil to remove the major portion of the gums therefrom to,form adegummed oil, adding an amount of the original undegummed oil tosaid degummed oil sufficient to bring the amount of gums in theresultant oil to a predetermined minimum amount which will causeeffectlve separation of soap stock from neutral oil cludingphosphatides, which comprises, mixing agum-precipitating reagent withsaid oil, separating the precipitated gums from said oil, thereafter mng said oilwith suflicient undegummed oil to cause effective separationof soap stock from the oil during subsequent alkali refining, thereaftermixing an alkali refining reagent with said oil. to form a mixture ofoil and soap stock and separating the said soap stock from said oil.

4. The process of refining vegetable oils from which minor constituentsincluding phosphatides have been separated and recovered, whichcomprises, mixing said oil with a similar oil containing gums,thereafter adding an alkali refining reagent to said oil to form, amixture of oil and soap stock including said gums, and separating saidsoap stockfrom said oil. f

5. In the process of alkali refining degummed oil, in which an alkalirefining reagent is added to said oil and the resulting soap stock sepa-I rated from said oil, the improvement which comprises adding sufiicientoil containing gums to said degummed oil during said process to causesaid soap stock to" contain sufllcient gums to prevent stratiflcationthereof, whereby said soap' stock can be cleanly separated from saidoil.

6. In a process of alkali refining degummed vegetable oils containingfree fatty acids, said process including adding an alkali refiningreagent to said oil to neutralize said free fatty acids to thus form amixture of oil and soap stock and separating the said soap stock fromsaid oil, the improvement which comprises adding to said oil during saidprocess suflicient oil containing gums to cause said soap stock toseparate cleanly from the refined oil.

7. A process of alkali refining animal and vegetable oils containinggums and free fatty acids. which comprises, adding a similar oil havinga different gum content to adjust the gum content of said oil to anamount which will cause the soap stock produced in said processto'separate cleanly from the refined oil with a minimum entrainment ofneutral oil in said soap stock, adding an alkaline refining reagent tosaid oil in which the gum content has been adjusted in order to form amixture of soap stock and refined oil, and thereafter separating saidrefined oil from said soap stock.

8. In the process of refining animal and vegetable oils which includesthe steps of adding an alkali refining reagent to said oil andseparating the resulting soap stock from said 011, the improvement whichcomprises adding a similar oil having a difierent gum content to adjustthe gum content of said oil during said process to an amount which willcause clean separation of the,

soap stock from said oil at a minimum entrainment of oil in the saidsoap stock.

9. A continuous process of refining animal and vegetable oils, whichcomprises, continuously mixin a degumming reagent with said oil in anamo t sufilcient to cause precipitation of said gums and wet said oil,thereafter continuously centrifugally separating precipitated gums fromsaid oil at a temperature which facilitates such separation,continuously mixing sufiicient undegummed oil with the separated oil toadjust the gum content of the resulting mixture to a predeterminedpercentage which will cause efiective separation of soap stock fromrefined oil with a minimum oil entrainment in said soap stock when themixture of oil is subjected to alkali refining, continuously mixing analkali refining reagent with said mixture of oils, and thereaftercontinuously centrifugally separating the resulting soap stock fromrefined oil at an emulsion breaking temperature.

HOWARD M. DUvALL, James.

